Atmosphere‐Ocean CO2 Exchange Across the Last Deglaciation from the Boron Isotope Proxy

Type Article
Date 2019-10
Language English
Author(s) Shao Jun1, Stott Lowell D.1, Gray William R.2, 3, Greenop Rosanna2, Pecher Ingo4, Neil Helen L.5, Coffin Richard B.6, Davy Bryan7, Rae James W.B.2
Affiliation(s) 1 : Department of Earth Science University of Southern California Los Angeles, USA
2 : School of Earth and Environmental Sciences, University of St Andrews St Andrews, UK
3 : Laboratoire des Sciences du Climat et de l’Environnement (LSCE/IPSL) Gif‐sur‐Yvette ,France
4 : School of Environment, University of Auckland Auckland, New Zealand
5 : Department of Marine Geologythe National Institute of Water and Atmospheric Research ,New Zealand
6 : Department of Physical and Environmental Sciences, Texas A M University‐Corpus Christi ,USA
7 : Department of Marine Geosciences, GNS Science ,New Zealand
Source Paleoceanography And Paleoclimatology (2572-4517) (American Geophysical Union (AGU)), 2019-10 , Vol. 34 , N. 10 , P. 1650-1670
DOI 10.1029/2018PA003498
WOS© Times Cited 14
Note Highlght : Research Spotlight—Oceans Vented Carbon Dioxide During the Last Deglaciation

Identifying processes within the Earth System that have modulated atmospheric pCO2 during each glacial cycle of the late Pleistocene stands as one of the grand challenges in climate science. The growing array of surface ocean pH estimates from the boron isotope proxy across the last glacial termination may reveal regions of the ocean that influenced the timing and magnitude of pCO2 rise. Here we present two new boron isotope records from the subtropical‐subpolar transition zone of the Southwest Pacific that span the last 20 kyr, as well as new radiocarbon data from the same cores. The new data suggest this region was a source of carbon to the atmosphere rather than a moderate sink as it is today. Significantly higher outgassing is observed between ~16.5‐14 kyrBP, associated with increasing δ13C and [CO3]2‐ at depth, suggesting loss of carbon from the intermediate ocean to the atmosphere. We use these new boron isotope records together with existing records to build a composite pH/pCO2 curve for the surface oceans. pH disequilibrium/CO2 outgassing was widespread throughout the last deglaciation, likely explained by upwelling of CO2 from the deep/intermediate ocean. During the Holocene, a smaller outgassing peak is observed at a time of relatively stable atmospheric CO2, which may be explained by regrowth of the terrestrial biosphere countering ocean CO2 release. Our stack is likely biased toward upwelling/CO2 source regions. Nevertheless, the composite pCO2 curve provides robust evidence that various parts of the ocean were releasing CO2 to the atmosphere over the last 25 kyr.

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Shao Jun, Stott Lowell D., Gray William R., Greenop Rosanna, Pecher Ingo, Neil Helen L., Coffin Richard B., Davy Bryan, Rae James W.B. (2019). Atmosphere‐Ocean CO2 Exchange Across the Last Deglaciation from the Boron Isotope Proxy. Paleoceanography And Paleoclimatology, 34(10), 1650-1670. Publisher's official version : , Open Access version :